A New Study Clarifies How Alcohol Causes Cancer

For Cancer Prevention Month, AICR is highlighting two urgent concerns: the strong evidence from AICR research on the direct link between alcohol consumption and increased risk for six cancer types and the national statistics on the rising trend of alcohol drinking across specific demographics in the US.

AICR’s Continuous Update Project reports show that alcohol raises risk for breast, esophageal, liver, colorectal, stomach and mouth/pharynx/larynx. The damage done by alcohol is becoming increasingly clear, and some of it has to do with damage at the cellular and genetic level. Now a recent study adds to the science explaining how alcohol plays a role in cancer risk.

A new study published in Nature in January throws light on how alcohol causes cancer. Scientists at the Medical Research Council Laboratory of Molecular Biology, Cambridge, gave alcohol, to mice. They then used chromosome analysis and DNA sequencing to examine the genetic damage caused by acetaldehyde, a chemical produced when the body processes alcohol. They found that acetaldehyde broke and damaged DNA within blood stem cells leading to rearranged chromosomes and permanently altering the DNA sequences within these cells. The damaged DNA blueprint within these stem cells can give rise to cancer.

The study also looked into the body’s natural defense to protect itself during alcohol metabolism. Routinely, the body produces an enzyme which helps to fix and reverse different types of DNA damage. The first line of defense is a family of enzymes called aldehyde dehydrogenases (ALDH). These enzymes break down harmful acetaldehydes into acetate, which are used as a source of energy.

But the problem of "defense" is complicated by genetic differences. Worldwide, millions of people either lack these enzymes (ALDH) or carry faulty versions of them and therefore are unable to completely break down acetaldehyde to protect the body against damage. In the above study, when mice lacking in critical ALDH enzyme -- ALDH2 -- were given alcohol, they showed four times as much DNA damage in their cells compared to mice with fully functioning ALDH2 enzymes. Even with the ALDH enzyme, you may not be completely protected. "The problem can be two-fold as far as our own body's defense against acetaldehyde is concerned: these enzymes don't always work and even if they do, the cells are not able to carry out the repairs effectively," explains Dr. Nigel Brockton, Director of Research at AICR.

While the science is becoming more clear on the risk, studies are finding evidence of rising alcohol consumption among women, older adults, racial/ethnic minorities and socioeconomically disadvantaged groups in the U.S. According to CDC, one in six US adults binge drinks about four times a month, consuming about eight drinks per binge. Binge drinking is defined as having four or more drinks on an occasion for women, or 5 or more drinks on an occasion for men. A study funded by the National Institute on Drug Abuse and the National Institute on Alcohol Abuse and Alcoholism found that there is a decline in binge drinking among American adolescents over the period from 1991 to 2015, but other studies show that there is evidence of rising alcohol consumption across demographics in the U.S.

The World Health Organization estimates that approximately between 4 percent and 25 percent of cancers are attributable to alcohol worldwide. According to The National Institute on Alcohol Abuse and Alcoholism, the leading agency in the United States for research on the health effects of alcohol, women who consume about one drink per day have a 5 - 9 percent higher chance of developing breast cancer than women that do not drink at all.

AICR’s Breast Cancer CUP report found that drinking the equivalent of a small glass of wine or beer a day (about 10 grams alcohol content) increases pre-menopausal breast cancer risk by 5 percent and post-menopausal breast cancer risk by 9 percent. A standard drink is 14 grams of alcohol.

For cancer prevention, AICR counsels not drinking alcohol. If you do drink alcohol, AICR recommends limiting consumption to no more than two drinks a day for men and one drink a day for women.

This research was funded by Cancer Research UK, Wellcome and the Medical Research Council (MRC).

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